This invention relates to the fabrication of integrated circuits. More particularly, this invention relates to integrated circuit testing.
In the manufacture of integrated circuits, such as semiconductor devices, the integrated circuits are typically formed on a substrate, such as a silicon wafer. During and after the fabrication process, the integrated circuit is tested to evaluate the electrical characteristics of the integrated circuit. One test method for flip-chip integrated circuits involves the use of probe cards having probes pins configured to align with contact pads of the integrated circuit. Probe cards generally include an electrically non conducting substrate having electrical traces that are in electrical communication with the probe pins, which are disposed one side of the substrate. A plurality of solder balls are typically disposed on the opposite side of the substrate for electrical communication with the tester.
The probe card is brought into contact with the integrated circuit using a probe station, or prober, with the probe pins contacting the electrical connections on the integrated circuit. The prober aligns the probe pins of the probe card with the electrical connections of the integrated circuit and applies force to the probe pins to obtain good electrical contact between the probe pins and the electrical connections of the integrated circuit, which are typically solder bumps. The probe pins are repeatedly pushed against integrated circuits during testing operations. The repeated force applied to the probe card during such testing tends to deform or warp the substrate of the probe card. Over time, this deformation of the planarity of the probe card substrate tends to inhibit the probe pins from making good electrical contact with the integrated circuits being tested.
What is needed, therefore, is a method for fabricating probe cards so that their substrates are more resistant to deformation, as compared to the substrates of conventional probe cards.
The above and other needs are met a probe card for testing an integrated circuit having electrical contacts. An interface member connects the probe card to a test station. An electrically non conducting substrate is provided with a first side, a second side, and electrically conducting traces. A plurality of electrically conducting probes are disposed adjacent the second side of the substrate. The probes make electrical connections with the traces, and the probes are also for making forceful contact and electrical connection with the electrical contacts of the integrated circuit.
Electrically conducting members are disposed between the first side of the substrate and the interface member. The electrically conducting members make electrical connection between the traces of the substrate and the interface member, and are disposed such that at least one void is formed between the first side of the substrate and the interface member. An electrically non conducting material is disposed within the at least one void, so as to substantially fill the at least one void. The electrically non conducting material reinforces the substrate against deformation during testing of the integrated circuit, when forceful contact is made between the probes and the electrical contacts of the integrated circuit.
Disposing electrically non-conducting material in the voids of the substrate in accordance with the present invention tends to substantially decrease the degree to which the substrate deforms during use. This results in improved testing and reduced costs.
In various preferred embodiments of the invention, the substrate is a glass filed plastic, and the electrically conducting members are solder bumps. The at least one void are then areas between the solder bumps. Preferably the electrically non conducting material within the .void is either an epoxy or a spacer, most preferably made of the same material as the substrate.